Isolated Process Current Input
with Loop Power
7B35
FEATURES
FUNCTIONAL BLOCK DIAGRAM
Single-channel signal conditioning current input module
that interfaces with two-wire transmitters.
Module provides a precision output of either +1 V to +5 V or
+2 V to +10 V, linear with temperature.
Features a isolated 24 VDC loop supply for driving the
transmitter.
All 7B35 series modules are mix-and-match and Hot
Swappable.
APPLICATIONS
Industrial signal isolation
Industrial signal filtering
PRODUCT OVERVIEW
The 7B Series of signal conditioners feature small size, low cost
and a wide output voltage range for a variety of applications
including process control and factory-floor environments. The
single-channel 7B modules accept inputs from a range of
transducers and are fully rated over the extended -40oC to
+85oC industrial temperature range. All 7B Series modules are
rated for a nominal power supply input of +24 VDC; and, for
maximum flexibility, they will accept supply voltages in the +14
VDC to +35 VDC range. The input modules, with the exception
of the 7B21, provide a high-level output voltage that is factory
configured for either the +1 V to +5 V or 0 V to +10 V range.
The 7B21 is a unity gain, isolated input module with an
input/output range of +10V. Output modules are available that
provide either isolated process current or isolated bipolar
voltage output. Model 7B39 converts either a +1 V to +5 V input
to a 4 to 20 mA output or a 0 V to +10 V input to a 0-20 mA
output. The input/output ranges of the 7B39 are factory
configured. The 7B22 is a unity gain module that provides an
isolated +10V output signal. All modules have a universal pinout and may be readily hot-swapped under full power without
disrupting field wiring. Each module accepts analog transducer
signals and transfers them to a process control or factory data
collection system without the inherent noise, non-linearity, drift
and extraneous voltages which frequently accompany the
signals.
Figure 1. 7B35 Functional Block Diagram
The modules feature a maximum nonlinearity of +0.02% and
are factory calibrated to guarantee a maximum accuracy
specification of +0.1%.
The 7B Series offers up to 1500 V rms continuous common
mode voltage isolation and 120 V rms of field wiring input
protection. The power supplies necessary to drive each of the
individual module’s input circuitry are internally isolated,
enabling the 7B Series modules to offer true channel-to-channel
isolation of the input signals.
The modules directly accept analog signals from
thermocouples, RTDs, current loop powered transmitters, and
other process control signals. The 7B Series modules amplify,
linearize, isolate, protect and convert the transducer output
signals to standardized analog inputs for high-level analog I/O
subsystems. The 7B Series Subsystem consists of 19-inch rackcompatible hardware (model AC 1363), with universal
mounting backplane and a family of plug-in (up to 16 per
backplane) input and output signal conditioning modules. Four, eight-, and sixteen-channel backplanes are available. Each
backplane incorporates screw terminals for easy power
connections and field wiring, and includes a 25-pin D-type
connector for interfacing the high-level single-ended voltage
outputs to the user’s equipment. Gold-plated sockets are
provided on each channel of the backplane to ensure the
reliability of each module’s electrical connection.
Rev. 0
Information furnished by Analog Devices is believed to be accurate and reliable.
However, no responsibility is assumed by Analog Devices for its use, nor for any
infringements of patents or other rights of third parties that may result from its use.
Specifications subject to change without notice. No license is granted by implication
or otherwise under any patent or patent rights of Analog Devices. Trademarks and
registered trademarks are the property of their respective companies.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
www.analog.com
Tel: 781.329.4700
Fax: 781.326.8703
© 2004 Analog Devices, Inc. All rights reserved.
7B35
GENERAL DESCRIPTION
isolated voltage provided by the 7B35 is between 13 VDC and
34 VDC for loop currents between 4 mA and 20 mA and supply
voltages between 20.4 VDC and 26.4 VDC. The output section
contains a two-pole low-pass filter (-3 dB @ 100 Hz), a buffer
amplifier and power oscillator. The two-pole output filter and
subsequent buffer ensures that a low noise, low impedance
(<1Ω) signal is available at the output to drive loads down to
2kΩ.
The 7B35 is a single-channel signal conditioning current input
module that interfaces with two-wire transmitters, providing an
isolated protected precision output of either +1 V to +5 V or +2
V to +10 V. Model 7B35 features an isolated 24 VDC loop power
supply for driving the transmitter. To accurately measure low
level signals in electrically noisy environments, 1500 V rms of
galvanic transformer-based isolation with a common mode
rejection (CMR) of 105 dB @ 50/60 Hz is provided. Rated to
operate with a nominal +24 VDC supply, Model 7B35 is mixand-match and hot-swappable with other 7B Series input
modules, so it can be inserted or removed from any socket in
the same backplane without disturbing system power.
The two input pins of Model 7B35 are each fully protected up to
120 V rms. The current input signal is converted to a voltage,
then filtered by a one-pole 100 Hz filter. Amplitude modulation
is used to implement transformer isolation (1500 V rms inputto-output and power). Isolated front-end circuitry power is
supplied by a DC/DC converter. The isolated transmitter loop
power supply is unregulated and will provide a voltage that is
proportional to the voltage used to power the 7B35 module. The
Figure 2
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7B35
7B35 Models Available
Model
Input Range
7B35-01-1
+4 mA to +20 mA1
7B35-01-2
1
Output Range
+1 V to +5 V
+4 mA to +20 mA
+2 V to +10 V
7B35 Specifications
(typical @ +23°C ±5°C and Vs = +24 V dc)
Description
Model 7B35
Input Range1
Standard Range
4 mA to 20 mA
Custom Ranges
Not Available*
Standard Range
4 mA to 20 mA
Custom Ranges
Not Available*
Input Loop Supply Voltage, Isolated
+24 V dc @ ILoop = 20 mA
Output Range (RL > 2 kΩ)
+1 V to +5 V or +2 V to +10 V
Accuracy1
Initial @ +25°C
2
±0.01% Span (±0.1% Span, maximum)
Nonlinearity
±0.02% Span, maximum
Input Offset vs. Temperature
N/A3
Span vs. Temperature
±40 ppm/°C
Output Offset vs. Temperature
±0.003% span/°C
Output Noise
5 MHz Bandwidth
6 mV peak
10 Hz to 100 kHz Bandwidth
0.9 mV rms
0.1 Hz to 10 Hz Bandwidth
4 µV peak
Bandwidth, -3 dB
100 Hz
Output Rise Time, 10% to 90% Span
5 ms
Common-Mode Voltage (CMV)
Input-to-Output and Power
1500 V rms continuous
Common Mode Rejection (CMR)
Input-to-Output and Power @ 50/60 Hz
105 dB
Input Protection
120 V rms, continuous
±35 V dc, continuous
Input Transient Protection
ANSI/IEEE C376.90.1-1989
IEEE-STD 472
IEC 255-4, Class II
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7B35
Output Resistance
<1Ω
Voltage Output Protection
Continuous Short to Ground
Power Supply
Voltage Range, Operating
+14 V dc to +35 V dc
Current
+25 mA, maximum
Sensitivity
±0.0001%/% of Vs
Mechanical Dimensions
1.663" x 2.11" x 0.563"
(42.24 mm x 53.6 mm x 14.3 mm)
Weight
60 grams
Environmental
Temperature Range
Operating
-40°C to +85°C
Storage
-40°C to +85°C
Relative Humidity, 24 hours
0 to 90% @ +60°C non-condensing
ESD Sensitivity
IEC 801-2, Level 2
RFI Susceptibility
±0.5% Span error @ 400 MHz, 5 Watt, 3 ft
Warm-up time required to meet specifications is approximately 10 minutes.
* Contact factory for OEM requirements.
1
Includes the combined effects of repeatability, hysteresis, and nonlinearity.
2
Nonlinearity is calculated using best-fit straight line method.
3
Input offset term is included in the output offset specification.
Specifications subject to change without notice.
Rev. 0 | Page 4 of 8
7B35
PIN CONFIGURATIONS AND FUNCTIONAL DESCRIPTIONS
Figure 3 7B35 Input Field Connections
Table 1. Pin Function Descriptions—
Pin
No.
0
1
2
3
4
5
Input Module Function
Output Module Function
SENSOR INPUT
INPUT HIGH
INPUT LOW
POWER SUPPLY (DC)
OUTPUT VOLTAGE
OUTPUT & POWER
COMMON
NOT USED
OUTPUT HIGH
OUTPUT LOW
POWER SUPPLY (DC)
INPUT VOLTAGE
INPUT AND POWER
COMMON
Figure 4 . Model 7B Series Module, with pin-out assignments.
ESD CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human
body and test equipment and can discharge without detection. Although this product features proprietary ESD
protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges.
Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.
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7B35
OUTLINE DIMENSIONS
Figure 5. Outline Dimensions
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7B35
NOTES
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7B35
NOTES
© 2004 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective companies.
D05177-0-10/04(0)
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